秦岭—大别东段应力状态研究

摘要/Abstract

摘要： 本文首先通过Snoke发展的利用P波、 SV波和SH波的初动和振幅比方法计算秦岭—大别东段2008年以来83次M_L≥2.5地震的震源机制解, 然后通过FMSI方法反演得到平均应力场的方向特征: 近东西向的水平挤压和近南北向的水平拉张作用, 与参数统计结果一致; 进而通过震源机制的一致性参数分析应力场方向的变化信息。分析表明震源机制解呈现了由变化紊乱、偏离平均应力场到变化一致、趋于平均应力场再到变化紊乱、偏离平均应力场的变化过程, 在显著地震前, 研究区整体的震源机制一致性参数处于持续低值状态; 计算了2008年以来93次M_L≥2.5地震的视应力, 拟合视应力与震级的关系, 分析扣除震级影响的差视应力随时间变化特征, 近似反映研究区应力大小的变化。分析表明显著地震前研究区的差视应力值呈现出明显的先上升后下降的变化过程, 在下降过程中发生地震; 最后利用震源机制一致性参数和差视应力综合分析研究区的应力状态, 均表明显著地震前震源区的构造应力场增强。目前研究区的震源机制一致性参数较高、差视应力较低, 研究区的应力水平较低。

关键词: 震源机制解, 应力场, 震源机制一致性参数, 视应力, 应力状态, 秦岭—大别东段

Abstract: Through the method developed by Snoke, which uses the ratio of initial motion and amplitude of P, SV and SH waves, we calculated the focal mechanism solution to 83 M_L≥2.5 earthquakes since 2008 in eastern Qinling—Dabie region. Based on these focal mechanisms, we inverted direction characteristic of the mean stress field using the FMSI method. The result shows that Qinling—Dabie eastern region is horizontally compressed in nearly E-W direction and horizontally dilated in nearly N-S direction, which is in accord with statistical results of focal mechanism parameters. We analyzed the variation information of the mean stress field direction through the consistency parameter of focal mechanisms, and the result shows that the focal mechanisms show a process from change in disorder and deviation from the mean stress field, to change in order and tendency to the mean stress field, then to change in disorder and deviation from the mean stress field. Consistency parameter of focal mechanisms in the studied region was in a continuous low value state before the significant earthquakes. Moreover, we calculated the apparent stress of 93 M_L≥2.5 earthquakes since 2008 in Qinling—Dabie eastern region, and fitted the relationship between apparent stress and magnitude, analyzed the time variation characteristic of the difference apparent stress that eliminated the effect of magnitude and reflected the variation of stress magnitude in the study area. The result shows that apparent stress in studied region showed a distinct process of first rising and then decreasing before significant earthquakes, and the significant earthquakes occurred during the process of decreasing. Finally, we analyzed the stress state in the study region by using consistency parameter of focal mechanism and difference apparent stress, and the result showed that regional stress field enhanced apparently before significant earthquakes. At present, the consistency parameter of focal mechanism in the study area is high, and difference apparent stress is low, so the regional stress level is low.

Key words: Focal mechanism solution, Stress field, Apparent stress, Stress state, Qinling—Dabie eastern

中图分类号:

P315.7

倪红玉, 刘泽民, 洪德全, 赵朋, 汪小厉. 秦岭—大别东段应力状态研究[J]. 地震, 2019, 39(3): 138-148.

NI Hong-yu, LIU Ze-min, HONG De-quan, ZHAO Peng, WANG Xiao-li. Study on Stress State in the East Section of Qinling—Dabie Mountains[J]. EARTHQUAKE, 2019, 39(3): 138-148.

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